// Copyright (c) 2015 Pyfisch
// https://github.com/ipld/serde_ipld_dagcbor/blob/379581691d82a68a774f87deb9462091ec3c8cb6/src/de.rs
//
// This is mostly a copy-paste of the original file, with the following changes:
// - strings are de-serialized as `BadStr`. This is a workaround for the historical
// bug in Lotus where malformed UTF-8 strings were serialized as CBOR strings.
// Allow everything so we don't stray from the original code too much.
#![allow(clippy::all, warnings)]

use self::cbor4ii_nonpub::*;
use cbor4ii::core::dec::{self, Decode};
use cbor4ii::core::types::BadStr;
use cbor4ii::core::utils::IoReader;
use cbor4ii::core::{major, types, utils::SliceReader};
use cid::serde::CID_SERDE_PRIVATE_IDENTIFIER;
use core::convert::Infallible;
use serde::de::{self, Visitor};
use serde_ipld_dagcbor::DecodeError;
use std::borrow::Cow;

// This module refers to the file:
// https://github.com/ipld/serde_ipld_dagcbor/blob/379581691d82a68a774f87deb9462091ec3c8cb6/src/cbor4ii_nonpub.rs
mod cbor4ii_nonpub {
    use super::*;
    use cbor4ii::core::dec;

    // Copy from cbor4ii/core.rs.
    #[allow(dead_code)]
    pub(crate) mod marker {
        pub const START: u8 = 0x1f;
        pub const FALSE: u8 = 0xf4; // simple(20)
        pub const TRUE: u8 = 0xf5; // simple(21)
        pub const NULL: u8 = 0xf6; // simple(22)
        pub const UNDEFINED: u8 = 0xf7; // simple(23)
        pub const F16: u8 = 0xf9;
        pub const F32: u8 = 0xfa;
        pub const F64: u8 = 0xfb;
        pub const BREAK: u8 = 0xff;
    }

    // Copy from cbor4ii/core/dec.rs.
    #[inline]
    pub(crate) fn peek_one<'a, R: dec::Read<'a>>(
        reader: &mut R,
    ) -> Result<u8, DecodeError<R::Error>> {
        let buf = match reader.fill(1)? {
            dec::Reference::Long(buf) => buf,
            dec::Reference::Short(buf) => buf,
        };
        let byte = buf.first().copied().ok_or(DecodeError::Eof)?;
        Ok(byte)
    }

    // Copy from cbor4ii/core/dec.rs.
    #[inline]
    pub(crate) fn pull_one<'a, R: dec::Read<'a>>(
        reader: &mut R,
    ) -> Result<u8, DecodeError<R::Error>> {
        let byte = peek_one(reader)?;
        reader.advance(1);
        Ok(byte)
    }
}

/// Decodes a value from CBOR data in a slice.
///
/// # Examples
///
/// De-serialize a `String`
///
/// ```
/// # use serde_ipld_dagcbor::de;
/// let v: Vec<u8> = vec![0x66, 0x66, 0x6f, 0x6f, 0x62, 0x61, 0x72];
/// let value: String = de::from_slice(&v[..]).unwrap();
/// assert_eq!(value, "foobar");
/// ```
///
/// De-serialize a borrowed string with zero copies.
///
/// ```
/// # use serde_ipld_dagcbor::de;
/// let v: Vec<u8> = vec![0x66, 0x66, 0x6f, 0x6f, 0x62, 0x61, 0x72];
/// let value: &str = de::from_slice(&v[..]).unwrap();
/// assert_eq!(value, "foobar");
/// ```
pub fn from_slice<'a, T>(buf: &'a [u8]) -> Result<T, DecodeError<Infallible>>
where
    T: de::Deserialize<'a>,
{
    let reader = SliceReader::new(buf);
    let mut deserializer = Deserializer::from_reader(reader);
    let value = serde::Deserialize::deserialize(&mut deserializer)?;
    deserializer.end()?;
    Ok(value)
}

/// Decodes a value from CBOR data in a reader.
///
/// # Examples
///
/// De-serialize a `String`
///
/// ```
/// # use serde_ipld_dagcbor::de;
/// let v: Vec<u8> = vec![0x66, 0x66, 0x6f, 0x6f, 0x62, 0x61, 0x72];
/// let value: String = de::from_reader(&v[..]).unwrap();
/// assert_eq!(value, "foobar");
/// ```
///
/// Note that `from_reader` cannot borrow data:
///
/// ```compile_fail
/// # use serde_ipld_dagcbor::de;
/// let v: Vec<u8> = vec![0x66, 0x66, 0x6f, 0x6f, 0x62, 0x61, 0x72];
/// let value: &str = de::from_reader(&v[..]).unwrap();
/// assert_eq!(value, "foobar");
/// ```
pub fn from_reader<T, R>(reader: R) -> Result<T, DecodeError<std::io::Error>>
where
    T: de::DeserializeOwned,
    R: std::io::BufRead,
{
    let reader = IoReader::new(reader);
    let mut deserializer = Deserializer::from_reader(reader);
    let value = serde::Deserialize::deserialize(&mut deserializer)?;
    deserializer.end()?;
    Ok(value)
}

/// A `serde` `Deserialize`r of DAG-CBOR data.
#[derive(Debug)]
struct Deserializer<R> {
    reader: R,
}

impl<R> Deserializer<R> {
    /// Constructs a `Deserializer` which reads from a `Read`er.
    pub fn from_reader(reader: R) -> Deserializer<R> {
        Deserializer { reader }
    }
}

impl<'de, R: dec::Read<'de>> Deserializer<R> {
    #[allow(clippy::type_complexity)]
    #[inline]
    fn try_step<'a>(
        &'a mut self,
    ) -> Result<scopeguard::ScopeGuard<&'a mut Self, fn(&'a mut Self) -> ()>, DecodeError<R::Error>>
    {
        if self.reader.step_in() {
            Ok(scopeguard::guard(self, |de| de.reader.step_out()))
        } else {
            Err(DecodeError::DepthLimit)
        }
    }

    #[inline]
    fn deserialize_cid<V>(&mut self, visitor: V) -> Result<V::Value, DecodeError<R::Error>>
    where
        V: Visitor<'de>,
    {
        let tag = dec::TagStart::decode(&mut self.reader)?;

        match tag.0 {
            CBOR_TAGS_CID => visitor.visit_newtype_struct(&mut CidDeserializer(self)),
            _ => Err(DecodeError::TypeMismatch {
                name: "CBOR tag",
                byte: tag.0 as u8,
            }),
        }
    }

    /// This method should be called after a value has been de-serialized to ensure there is no
    /// trailing data in the input source.
    pub fn end(&mut self) -> Result<(), DecodeError<R::Error>> {
        match peek_one(&mut self.reader) {
            Ok(_) => Err(DecodeError::TrailingData),
            Err(DecodeError::Eof) => Ok(()),
            Err(error) => Err(error),
        }
    }
}

macro_rules! deserialize_type {
    ( @ $t:ty , $name:ident , $visit:ident ) => {
        #[inline]
        fn $name<V>(self, visitor: V) -> Result<V::Value, Self::Error>
        where V: Visitor<'de>
        {
            let value = <$t>::decode(&mut self.reader)?;
            visitor.$visit(value)
        }
    };
    ( $( $t:ty , $name:ident , $visit:ident );* $( ; )? ) => {
        $(
            deserialize_type!(@ $t, $name, $visit);
        )*
    };
}

impl<'de, 'a, R: dec::Read<'de>> serde::Deserializer<'de> for &'a mut Deserializer<R> {
    type Error = DecodeError<R::Error>;

    fn deserialize_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        let mut de = self.try_step()?;
        let de = &mut *de;

        let byte = peek_one(&mut de.reader)?;
        if is_indefinite(byte) {
            return Err(DecodeError::IndefiniteSize);
        }
        match dec::if_major(byte) {
            major::UNSIGNED => de.deserialize_u64(visitor),
            major::NEGATIVE => de.deserialize_i64(visitor),
            major::BYTES => de.deserialize_byte_buf(visitor),
            major::STRING => de.deserialize_string(visitor),
            major::ARRAY => de.deserialize_seq(visitor),
            major::MAP => de.deserialize_map(visitor),
            // The only supported tag is tag 42 (CID).
            major::TAG => de.deserialize_cid(visitor),
            major::SIMPLE => match byte {
                marker::FALSE => {
                    de.reader.advance(1);
                    visitor.visit_bool(false)
                }
                marker::TRUE => {
                    de.reader.advance(1);
                    visitor.visit_bool(true)
                }
                marker::NULL => {
                    de.reader.advance(1);
                    visitor.visit_none()
                }
                marker::F32 => de.deserialize_f32(visitor),
                marker::F64 => de.deserialize_f64(visitor),
                _ => Err(DecodeError::Unsupported { byte }),
            },
            _ => Err(DecodeError::Unsupported { byte }),
        }
    }

    deserialize_type!(
        bool,       deserialize_bool,       visit_bool;

        i8,         deserialize_i8,         visit_i8;
        i16,        deserialize_i16,        visit_i16;
        i32,        deserialize_i32,        visit_i32;
        i64,        deserialize_i64,        visit_i64;
        i128,       deserialize_i128,       visit_i128;

        u8,         deserialize_u8,         visit_u8;
        u16,        deserialize_u16,        visit_u16;
        u32,        deserialize_u32,        visit_u32;
        u64,        deserialize_u64,        visit_u64;
        u128,       deserialize_u128,       visit_u128;

        f32,        deserialize_f32,        visit_f32;
        f64,        deserialize_f64,        visit_f64;
    );

    #[inline]
    fn deserialize_char<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        // Treat it as a String.
        // This is a bit wasteful when encountering strings of more than one character,
        // but we are optimistic this is a cold path.
        self.deserialize_str(visitor)
    }

    #[inline]
    fn deserialize_bytes<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        match <types::Bytes<Cow<[u8]>>>::decode(&mut self.reader)?.0 {
            Cow::Borrowed(buf) => visitor.visit_borrowed_bytes(buf),
            Cow::Owned(buf) => visitor.visit_byte_buf(buf),
        }
    }

    #[inline]
    fn deserialize_byte_buf<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        self.deserialize_bytes(visitor)
    }

    #[inline]
    fn deserialize_str<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        match <BadStr<Cow<[u8]>>>::decode(&mut self.reader)?.0 {
            Cow::Borrowed(buf) => visitor.visit_borrowed_bytes(buf),
            Cow::Owned(buf) => visitor.visit_bytes(&buf),
        }
    }

    #[inline]
    fn deserialize_string<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        self.deserialize_str(visitor)
    }

    #[inline]
    fn deserialize_option<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        let byte = peek_one(&mut self.reader)?;
        if byte != marker::NULL {
            let mut de = self.try_step()?;
            visitor.visit_some(&mut **de)
        } else {
            self.reader.advance(1);
            visitor.visit_none()
        }
    }

    #[inline]
    fn deserialize_unit<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        let byte = pull_one(&mut self.reader)?;
        if byte == marker::NULL {
            visitor.visit_unit()
        } else {
            Err(DecodeError::TypeMismatch { name: "unit", byte })
        }
    }

    #[inline]
    fn deserialize_unit_struct<V>(
        self,
        _name: &'static str,
        visitor: V,
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        self.deserialize_unit(visitor)
    }

    #[inline]
    fn deserialize_newtype_struct<V>(
        self,
        name: &'static str,
        visitor: V,
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        if name == CID_SERDE_PRIVATE_IDENTIFIER {
            self.deserialize_cid(visitor)
        } else {
            visitor.visit_newtype_struct(self)
        }
    }

    #[inline]
    fn deserialize_seq<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        let mut de = self.try_step()?;
        let seq = Accessor::array(&mut de)?;
        visitor.visit_seq(seq)
    }

    #[inline]
    fn deserialize_tuple<V>(self, len: usize, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        let mut de = self.try_step()?;
        let seq = Accessor::tuple(&mut de, len)?;
        visitor.visit_seq(seq)
    }

    #[inline]
    fn deserialize_tuple_struct<V>(
        self,
        _name: &'static str,
        len: usize,
        visitor: V,
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        self.deserialize_tuple(len, visitor)
    }

    #[inline]
    fn deserialize_map<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        let mut de = self.try_step()?;
        let map = Accessor::map(&mut de)?;
        visitor.visit_map(map)
    }

    #[inline]
    fn deserialize_struct<V>(
        self,
        _name: &'static str,
        _fields: &'static [&'static str],
        visitor: V,
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        self.deserialize_map(visitor)
    }

    #[inline]
    fn deserialize_enum<V>(
        self,
        _name: &'static str,
        _variants: &'static [&'static str],
        visitor: V,
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        let mut de = self.try_step()?;
        let accessor = EnumAccessor::enum_(&mut de)?;
        visitor.visit_enum(accessor)
    }

    #[inline]
    fn deserialize_identifier<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        self.deserialize_str(visitor)
    }

    #[inline]
    fn deserialize_ignored_any<V>(self, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        let _ignore = dec::IgnoredAny::decode(&mut self.reader)?;
        visitor.visit_unit()
    }

    #[inline]
    fn is_human_readable(&self) -> bool {
        false
    }
}

struct Accessor<'a, R> {
    de: &'a mut Deserializer<R>,
    len: usize,
}

impl<'de, 'a, R: dec::Read<'de>> Accessor<'a, R> {
    #[inline]
    pub fn array(de: &'a mut Deserializer<R>) -> Result<Accessor<'a, R>, DecodeError<R::Error>> {
        let array_start = dec::ArrayStart::decode(&mut de.reader)?;
        array_start.0.map_or_else(
            || Err(DecodeError::IndefiniteSize),
            move |len| Ok(Accessor { de, len }),
        )
    }

    #[inline]
    pub fn tuple(
        de: &'a mut Deserializer<R>,
        len: usize,
    ) -> Result<Accessor<'a, R>, DecodeError<R::Error>> {
        let array_start = dec::ArrayStart::decode(&mut de.reader)?;

        if array_start.0 == Some(len) {
            Ok(Accessor { de, len })
        } else {
            Err(DecodeError::RequireLength {
                name: "tuple",
                expect: len,
                value: array_start.0.unwrap_or(0),
            })
        }
    }

    #[inline]
    pub fn map(de: &'a mut Deserializer<R>) -> Result<Accessor<'a, R>, DecodeError<R::Error>> {
        let map_start = dec::MapStart::decode(&mut de.reader)?;
        map_start.0.map_or_else(
            || Err(DecodeError::IndefiniteSize),
            move |len| Ok(Accessor { de, len }),
        )
    }
}

impl<'de, 'a, R> de::SeqAccess<'de> for Accessor<'a, R>
where
    R: dec::Read<'de>,
{
    type Error = DecodeError<R::Error>;

    #[inline]
    fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Self::Error>
    where
        T: de::DeserializeSeed<'de>,
    {
        if self.len > 0 {
            self.len -= 1;
            Ok(Some(seed.deserialize(&mut *self.de)?))
        } else {
            Ok(None)
        }
    }

    #[inline]
    fn size_hint(&self) -> Option<usize> {
        Some(self.len)
    }
}

impl<'de, 'a, R: dec::Read<'de>> de::MapAccess<'de> for Accessor<'a, R> {
    type Error = DecodeError<R::Error>;

    #[inline]
    fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Self::Error>
    where
        K: de::DeserializeSeed<'de>,
    {
        if self.len > 0 {
            self.len -= 1;
            Ok(Some(seed.deserialize(&mut *self.de)?))
        } else {
            Ok(None)
        }
    }

    #[inline]
    fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Self::Error>
    where
        V: de::DeserializeSeed<'de>,
    {
        seed.deserialize(&mut *self.de)
    }

    #[inline]
    fn size_hint(&self) -> Option<usize> {
        Some(self.len)
    }
}

struct EnumAccessor<'a, R> {
    de: &'a mut Deserializer<R>,
}

impl<'de, 'a, R: dec::Read<'de>> EnumAccessor<'a, R> {
    #[inline]
    pub fn enum_(
        de: &'a mut Deserializer<R>,
    ) -> Result<EnumAccessor<'a, R>, DecodeError<R::Error>> {
        let byte = peek_one(&mut de.reader)?;
        match dec::if_major(byte) {
            // string
            major::STRING => Ok(EnumAccessor { de }),
            // 1 length map
            major::MAP if byte == (major::MAP << 5) | 1 => {
                de.reader.advance(1);
                Ok(EnumAccessor { de })
            }
            _ => Err(DecodeError::TypeMismatch { name: "enum", byte }),
        }
    }
}

impl<'de, 'a, R> de::EnumAccess<'de> for EnumAccessor<'a, R>
where
    R: dec::Read<'de>,
{
    type Error = DecodeError<R::Error>;
    type Variant = EnumAccessor<'a, R>;

    #[inline]
    fn variant_seed<V>(self, seed: V) -> Result<(V::Value, Self::Variant), Self::Error>
    where
        V: de::DeserializeSeed<'de>,
    {
        let variant = seed.deserialize(&mut *self.de)?;
        Ok((variant, self))
    }
}

impl<'de, 'a, R> de::VariantAccess<'de> for EnumAccessor<'a, R>
where
    R: dec::Read<'de>,
{
    type Error = DecodeError<R::Error>;

    #[inline]
    fn unit_variant(self) -> Result<(), Self::Error> {
        Ok(())
    }

    #[inline]
    fn newtype_variant_seed<T>(self, seed: T) -> Result<T::Value, Self::Error>
    where
        T: de::DeserializeSeed<'de>,
    {
        seed.deserialize(&mut *self.de)
    }

    #[inline]
    fn tuple_variant<V>(self, len: usize, visitor: V) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        use serde::Deserializer;

        self.de.deserialize_tuple(len, visitor)
    }

    #[inline]
    fn struct_variant<V>(
        self,
        _fields: &'static [&'static str],
        visitor: V,
    ) -> Result<V::Value, Self::Error>
    where
        V: Visitor<'de>,
    {
        use serde::Deserializer;

        self.de.deserialize_map(visitor)
    }
}

/// De-serialize a DAG-CBOR encoded CID.
///
/// This is without the CBOR tag information. It is only the CBOR byte string identifier (major
/// type 2), the number of bytes, and a null byte prefixed CID.
///
/// The reason for not including the CBOR tag information is the `Value` implementation. That one
/// starts to parse the bytes, before we could interfere. If the data only includes a CID, we are
/// parsing over the tag to determine whether it is a CID or not and go from there.
struct CidDeserializer<'a, R>(&'a mut Deserializer<R>);

impl<'de, 'a, R: dec::Read<'de>> de::Deserializer<'de> for &'a mut CidDeserializer<'a, R> {
    type Error = DecodeError<R::Error>;

    fn deserialize_any<V: de::Visitor<'de>>(self, _visitor: V) -> Result<V::Value, Self::Error> {
        Err(de::Error::custom(
            "Only bytes can be deserialized into a CID",
        ))
    }

    #[inline]
    fn deserialize_bytes<V: de::Visitor<'de>>(self, visitor: V) -> Result<V::Value, Self::Error> {
        let byte = peek_one(&mut self.0.reader)?;
        match dec::if_major(byte) {
            major::BYTES => {
                // CBOR encoded CIDs have a zero byte prefix we have to remove.
                match <types::Bytes<Cow<[u8]>>>::decode(&mut self.0.reader)?.0 {
                    Cow::Borrowed(buf) => match buf.split_first() {
                        Some((0, rest)) => visitor.visit_borrowed_bytes(rest),
                        _ => Err(DecodeError::Msg("Invalid CID".into())),
                    },
                    #[allow(clippy::indexing_slicing)]
                    Cow::Owned(mut buf) => {
                        if buf.len() <= 1 || buf[0] != 0 {
                            Err(DecodeError::Msg("Invalid CID".into()))
                        } else {
                            buf.remove(0);
                            visitor.visit_byte_buf(buf)
                        }
                    }
                }
            }
            _ => Err(DecodeError::Unsupported { byte }),
        }
    }

    fn deserialize_newtype_struct<V: de::Visitor<'de>>(
        self,
        name: &str,
        visitor: V,
    ) -> Result<V::Value, Self::Error> {
        if name == CID_SERDE_PRIVATE_IDENTIFIER {
            self.deserialize_bytes(visitor)
        } else {
            Err(de::Error::custom([
                "This deserializer must not be called on newtype structs other than one named `",
                CID_SERDE_PRIVATE_IDENTIFIER,
                "`"
            ].concat()))
        }
    }

    serde::forward_to_deserialize_any! {
        bool byte_buf char enum f32 f64 i8 i16 i32 i64 identifier ignored_any map option seq str
        string struct tuple tuple_struct u8 u16 u32 u64 unit unit_struct
    }
}

/// Check if byte is a major type with indefinite length.
#[inline]
pub fn is_indefinite(byte: u8) -> bool {
    byte & marker::START == marker::START
}